The invention relates to a mechanism that improves the operation of an intelligent network for setting up calls and producing services for the subscriber.
FIG. 1A shows the parts of prior art call set-up essential to the invention. A call is transmitted from A subscriber to B subscriber. A subscriber may be, for example, a user of an ordinary subscriber unit, a subscriber of a public branch exchange network PBX1 or a mobile subscriber connected via a mobile station exchange PLMN (Public Land-based Mobile Network) and a base station subsystem BSS. A call may be transmitted e.g. from A subscriber via the first exchange PBX1, a first exchange EXC1, a public integrated services network PISN, a second exchange EXC2 and a second exchange PBX2 to B subscriber. The exchange EXC1 or EXC2 is the most important part of FIG. 1 for the invention.
By means of an intelligent network (IN), a subscriber of a telecommunication networkxe2x80x94such as a wired network or a mobile telephone networkxe2x80x94is provided with a great number of different services. These services are e.g., a private numbering plan PNP, which enables the use of private numbers, and,a personal number in which users can only call to subscribers belonging to the same group. A specific numbering block is defined for PBX subscribers in the numbering domain of the exchange. One example of this kind of an intelligent network is described in recommendations of ITU-T Q-1200 series, of which Q-1210-Q-1219 define the set of features which is known as capability set 1 and correspondingly, Q-1220-Q-1229 define the set of features known as capability set 2. In the present invention, an improvement is put forth to the call set-up mechanism presented in recommendation Q-1214. The invention utilizes the solution shown in AIN Release 2 for setting up several controlling connections, making it compatible with capability set 2 architecture and entities.
The basic call state model BCSM defined in connection with the intelligent network describes different stages of call control and includes the places where call control can be interrupted for starting an intelligent network service. It identifies the event detection points in the call and connection process where service logic entities of the intelligent network can have an interactive relationship with basic call and connection management features.
Referring now to FIG. 1B, at the exchange, call set-up is divided into two parts, the call set-up at the input side and the call set-up at the output side. Input and output sides are collectively referred to as half-calls or call controls. Call control at the input side is connected to services of A subscriber and call control at the output side is connected to services of B subscriber. Corresponding state models are O-BCSM=Originating Basic Call State Model and T-BCSM=Terminating Basic Call State Model. A CS (CallSegment) corresponds to one call. A Feature Interaction Manager FIM is drawn between the state models O-BCSM/T-BCSM and the call segments CS. In conventional call set-up, without the help of an intelligent network, exchanges make independently all the deductions relating to call routing. Intelligent network architecture includes one or more service control points (SCP) which are also known as SCF elements (Service Control Function). An SCF element gives call set-up instructions to the exchange, or the exchange may ask the. SCF element for call set-up instructions, in which case it controls either one or both of the call segments CS, that is, either the output side or the input side. This is called a controlling connection. In FIG. 1B this is illustrated with a two-way arrow underneath the SCF. Only one SCF can control one half-call by a controlling connection. A controlling connection means that there is an ongoing session between the half-call and the SCF and at this session the SCF may give instructions that will change the call set-up. This means that there is an ongoing call, it has a TCAP connection (Transaction Capabilities Application Part) and by means of it additional information can be inquired or additional instructions can be received. The controlling connection may, have an effect on call set-up. Therefore, if at some stage of the call set-up, the interface of B subscriber is found to be busy, the call can be directed to an alternative number, for example.
A problem with capability set 1 and capability set 2 intelligent network architecture is that no more than one active, controlling connection can be associated with the same half-call. A practical example of such services could be a private numbering plan or a personal number. Two or more of these services cannot thus be activated by known intelligent network mechanisms for one half-call (for the same exchange) at the same time. The problem it causes to the provider and user of the service is that specific types of services cannot be implemented for the same subscriber at the same exchange at the same time.
As according to prior art, only one controlling connection may be associated with an incoming or outgoing call, a straightforward solution would be to establish such a state model where the incoming and/or outgoing half-call is associated with several controlling connections, that is, connections to the intelligent network service control point SCF. The problem with this straightforward solution is, however, that it would result in several changes to the software of the exchange as the state model of the call would have to be changed.
The object of the invention is thus to develop a method for producing services so that the aforementioned problems associated with production of several simultaneous services can be solved. The objects of the invention are attained with the method which is characterized by what is stated in the characterizing part of claim 1. The dependent claims relate to the preferred embodiments of the invention.
The basic idea of the invention is that in the call control mechanism, a connection is not necessarily directed to the outgoing half-call or to the next network element, but an incoming call can be circulated within the same exchange a number of times equalling the number of controlling connections needed to the intelligent network. The same idea can be expressed and realized also so that in the call control mechanism of the exchange, call state models, that is, pairs of virtual half-calls, are duplicated. A controlling connection and thus a different service may be associated with each virtual half-call.
By duplicating call state models (instead of several controlling connections being derived from one state model), specific advantages are attained. First, the art of the invention requires only small changes to the software of the exchange as it is easier to duplicate the same kind of state models than to form a new state model from which several controlling connections can be derived. The mechanism of the invention does not require changes to the interfaces of the state models because existing state modelsxe2x80x94software and data elementsxe2x80x94can be used essentially as such. The reliability of the exchange will be improved by keeping the changes small and by restricting them to accurately specified areas in comparison with a solution where a completely new state model were established. The mechanism of the invention can also be expanded easily as the number of controlling connections has no fixed upper limit.
The practical implementation of the invention can be further simplified if it is found out that instead of duplicating state model O-BCSM and/or T-BSCM, only the call segments CS can be duplicated. The duplication of only the speech segments is simpler (consumes less resources) than the duplication of whole state models.